The aim of this research project is to investigate cultural differences in reasoning about psychological contradiction and the role of dialectical thinking (Peng & Nisbett, 1999) in elucidating East-West differences in mental health. Dialectical thinking is a cultural variable that is rooted in East Asian philosophical and religious traditions. It is based on three primary tenets: the principle of contradiction (Yin/yang: two opposing propositions may both be true), the principle of change (the universe is in flux and is constantly changing), and the principle of holism (all things in the universe are interrelated). Contemporary dialectical thought is embedded within the lay cultural belief systems of numerous East Asian cultures, including Chinese, Japanese, Koreans, and Americans of East Asian background. A well-documented finding in the psychological literature is that East Asian cultures and East Asian minority group members exhibit poorer psychological adjustment than do Western cultures. We propose that dialectical thinking accounts, in large part, for the observed East-West variance in psychological adjustment. Because East Asians more readily accept psychological contradiction, including evaluative contradiction regarding the self, they exhibit more ambivalent or evaluatively inconsistent mental health and well-being judgments (Spencer-Rodgers, Peng, Wang, & Hou, 2004). In the proposed research, we will conduct a series of studies that examine the effects of dialectical thinking on psychological adjustment (at the University of California, Berkeley and Peking University, Beijing, China). The methodologies employed in the proposed research include questionnaire-based studies and experimental studies. The primary cultural groups examined in this research include Chinese (Beijing, China), Asian Americans, and European Americans. Across all six studies, Chinese and Asian Americans are expected to exhibit more evaluatively inconsistent self-beliefs than do European Americans. The proposed project will contribute to our understanding of the cultural and social factors that influence mental health outcomes. The studies go beyond an examination of simple categorical or group-level differences, to an investigation of the underlying cultural variable (dialectical thinking) and cognitive mechanisms that gives rise to the observed cross-cultural differences. This research is part of a growing concern for identifying the cultural factors involved in the etiology of psychological ill health.